1. Field of the Invention
The present invention relates to a dielectric ceramic composition and a multilayer ceramic capacitor having the same, and more particularly, to a dielectric ceramic composition having a high dielectric constant and superior high-temperature reliability and a multilayer ceramic capacitor having the same.
2. Description of the Related Art
In general, ceramic electronic components using ceramic materials, for example, capacitors, inductors, piezoelectric devices, varistors, or thermistors, include a ceramic sintered body made of ceramic materials, inner electrodes provided inside the ceramic sintered body, and outer electrodes provided on the surfaces of the ceramic sintered body to contact the inner electrodes.
As one of various ceramic electronic components, a multilayer ceramic capacitor includes a plurality of stacked dielectric layers, inner electrodes facing each other in which each pair of inner electrodes has one of the dielectric layers interposed therebetween, and outer electrodes electrically connected to the inner electrodes.
Multilayer ceramic capacitors are being widely used in mobile communications devices, such as laptop computers, PDAs mobile phones and the like, due to their compactness, high capacitance and ease of mounting.
A multi-layer ceramic capacitor is usually manufactured by stacking a paste for inner electrodes and a paste for dielectric layers using a sheet method, a printing method, or the like and co-firing the stack.
When a dielectric material used in a conventional multilayer ceramic capacitor is fired in a reduction atmosphere, it is reduced to thereby have semiconductive properties. For this reason, a material used for inner electrodes employs precious metals such as Pd that are not melted at a sintering temperature of the dielectric material and are not oxidized even when fired under the condition of high oxygen partial pressure, the condition in which the dielectric material is not to be semiconductive.
However, since precious metals such as Pd are expensive, this disturbs the achievement of low manufacturing costs of multilayer ceramic capacitors. Therefore, a base metal such as Ni or a Ni alloy, which is relatively cheap, is mainly used as a material for the inner electrodes. However, in the case where the base metal is used as a conductive material for the inner electrodes, when firing is performed at the ambient temperature, the inner electrodes are oxidized. Therefore, the co-firing of the dielectric layers and the inner electrodes are required to be performed in a reduction atmosphere.
However, when the firing is performed in a reduction atmosphere, the dielectric layers are reduced to thereby decrease insulation resistance (IR). Accordingly, a non-reducing dielectric material is being proposed. Also, there is an increase in demand for a dielectric ceramic composition for temperature compensation which has a small temperature coefficient of capacitance (TCC) and is controllable in the range of approximately −150 ppm/° C. and +150 ppm/° C.